Dispensing tool assembly for charging a refrigerant into a system

ABSTRACT

A tubular body supports a fluid actuated tubular piston connected to operate a coupling mechanism for releasably securing the body to a valve fitting on a refrigerant receiving system. The body encloses components which define a center passage connected to the fitting for first evacuating air from the system and then for directing liquid refrigerant into the system. The passage receives an elongated valve opening member which is fluid actuated to a position opening the valve fitting, and a movable valve member closes the passage to the flow of refrigerant. The fluid actuated coupling mechanism provides for convenient and simple insertion of the tool assembly onto the fitting with no insertion force and also for automatic release of the tool assembly from the fitting after charging is completed. A fluid actuated valve member minimizes the volume of residue refrigerant which vaporizes when the tool assembly is removed from the fitting.

BACKGROUND OF THE INVENTION

In equipment for charging a liquid refrigerant into a refrigeration orair conditioning system, for example, as disclosed in U.S. Pat. No.3,538,961 and No. 4,032,041, and particularly in equipment for chargingair conditioning systems for motor vehicles on an assembly line, it iscommon to couple the system first to a vacuum pump unit and then to aliquid refrigerant dispensing unit. The vacuum pump is used to evacuateair from the system after which the liquid refrigerant is dispensed orcharged into the system to a predetermined volume.

As disclosed in above U.S. Pat. No. 3,538,961, a suction line and aliquid refrigerant dispensing or charging line are coupled to the systemwith manually actuated quick-connect couplings each of which encloses avalve member or element movable from a normally closed position to anopen position when the coupling is attached to a male process fittinghaving an internal check or stem valve and connected to the system. Inmore recent years, both the suction line and the refrigerant supply lineare connected by a single coupling which connects with a single valvefitting on the system. The system is first evacuated through the fittingand coupling and then the liquid refrigerant is charged into the systemthrough the fitting. The single quick-connect coupling is particularlydesirable in an automotive production line since less time is requiredto connect and disconnect one coupling in place of two couplings.

In an automotive production line, it has been found desirable for thequick-connect coupling to be attached or connected to the processfitting with a minimum time and effort and also for the coupling to beautomatically disconnected from the fitting after the system has beencharged with refrigerant. It has also been found desirable for thecoupling to be compact in size and to be quickly connectable to theprocess fitting without requiring precise alignment between the couplingand the fitting. These desirable features minimize the operator's timeand eliminate the need for the operator to disconnect the coupling fromthe fitting at the end of the charging cycle. It has also been foundimportant to minimize the release of refrigerant vapor or gas when thecoupling is disconnected from the valve fitting.

SUMMARY OF THE INVENTION

The present invention is directed to an improved dispensing toolassembly which provides all of the desirable features mentioned above,and particularly for quickly and conveniently connecting anddisconnecting an evacuation line and a refrigerant supply or chargingline to a refrigerant system. More specifically, the invention isdirected to a dispensing tool assembly which may be connected to aprocess fitting on the system with no significant insertion force oreffort and which automatically releases from the fitting after thecharging cycle is completed.

The dispensing tool assembly of the invention also provides forautomatically closing the refrigerant supply passage adjacent thefitting when the charging cycle is completed so that no significantvolume of liquid refrigerant vaporizes into the air when the toolassembly is removed from the fitting. In addition, the dispensing toolassembly of the invention provides for a fitting seal which becomestighter as the pressure of the liquid refrigerant increases and foreliminating the need for precision alignment with the fitting during thecoupling and uncoupling operations. The dispensing tool assembly of theinvention further provides the manually disconnecting the tool assemblyfrom the fitting and for positive ejection of the tool assembly from thefitting.

Other features and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a dispensing tool assembly constructedin accordance with one embodiment of the invention;

FIG. 2 is an axial section of the tool assembly shown in FIG. 1 as it isbeing inserted onto a fitting of a refrigerant system;

FIG. 3 is a section taken generally on the line 3--3 of FIG. 1;

FIG. 4 is a fragmentary axial section similar to FIG. 2 and illustratingthe tool assembly after it is coupled to the fitting;

FIG. 5 is a fragmentary axial section similar to FIG. 4 and illustratingthe tool assembly during the evacuation and charging operations;

FIG. 6 is a fragmentary section similar to FIG. 5 and showing the toolassembly after ejection from the fitting;

FIG. 7 is an elevational view of a dispensing tool assembly constructedin accordance with another embodiment of the invention;

FIG. 8 is an enlarged plan view taken generally on the line 8--8 of FIG.7;

FIG. 9 is an enlarged axial section of the tool assembly as takengenerally on the line 9--9 of FIG. 8; and

FIG. 10 is a section taken generally on line 10--10 of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The dispensing tool assembly 15 shown in FIG. 1 is connected by afitting 16 and flexible high pressure hose 17 to refrigerant chargingequipment or apparatus, similar to that disclosed in above mentionedU.S. Pat. No. 3,538,961 and the tool assembly 15 replaces thequick-connect couplings 31 and 34 shown in the patent. The tool assembly15 is adapted to receive a conventional tubular valve fitting 20 whichprojects from a tank or line 21 forming part of an air conditioningsystem for a motor vehicle and which is first evacuated and then chargedwith liquid refrigerant through the tool assembly 15. The fitting 20 hasan external groove 23 and an internal spring biased valve stem member orelement 24.

Referring to FIG. 2, the tool assembly 15 includes a tubular body 26having a generally cylindrical outer portion or section 28 with anoutwardly projecting top flange 29 connected to a head portion 31 and adisk portion 32 by peripherally spaced screws 33 (FIG. 3). A tubularfitting 34 has a bottom flange 36 which is connected to the head portion31 by a set of screws 37 (FIG. 3). The outer section 28 of the body 26surrounds an inner generally cylindrical portion or section 42 which isspaced from the outer section 28 by upper and lower sets ofcircumferentially spaced ribs (not shown) to define an annular fluidpassage 46 between the cylindrical sections 28 and 42. Pressurizedactuating air is supplied to the passage 46 through an air actuatingline (not shown) connected to an internally threaded port 48 and througha connecting passage 49 formed within the upper portions 31 and 32 ofthe body 26.

The lower portion of the tubular body 26 supports a coupling assembly 52which includes a tubular piston 54 supported for axial sliding movementwithin the outer cylindrical section 28 of the body 26. A cylindricalsleeve 56 extends through the piston 54 and has an upper flange 57 whichengages an inwardly projecting flange 59 on the lower end of the innercylindrical section 42 of the body 26. A set of resilient O-rings 62 and63 form fluid-tight seals between the piston 54 and the sleeve 56 andouter body section 28, and other O-rings are used throughout the toolassembly and shown in FIGS. 2 and 4-6 but are not identified withreference numbers. The lower end flange portion 59 of the inner bodysection 42 cooperates with the upper portion of the piston 54 to definean annular fluid chamber 66 which receives pressurized air through thepassage 46 to move the piston 54.

The sleeve 56 has an inner diameter slightly larger than the outerdiameter of the fitting 20, and the lower end portion of the sleeve hasa series of circumferentially spaced holes which retain correspondingballs 69. An annular tapered surface 72 is formed within the lower endportion of the piston 54 and is effective to cam the balls 69 inwardlyinto the groove 23 of the fitting 20 when the piston 54 moves downwardlyfrom its retracted position (FIG. 2) to its extended position (FIG. 4)for locking the tool assembly 15 to the fitting 20. The piston 54 movesdownwardly in response to pressurized air supplied to the port 48, and acompression coil spring 74 returns the piston 54 to its retractedposition when the pressurized air is released.

The spring 74 extends between a flange on the piston 54 and the lowerend portion of a tubular collar 76 slidably supported by the outercylindrical section 28 of the body 26. The collar 76 has a knurled outersurface and is retained on the outer section 28 by a series of flexibleplastic strips 78 which are inserted through an opening 81 within thecollar 76. The strips are confined within opposing annular grooves 83and 84 within the body section 28 and collar 76 respectively. The axialwidth of the groove 83 is greater than the width of the groove 84 sothat the strips 78 may travel upwardly within the groove 83 when thecollar 76 is manually retracted upwardly against the force of the spring74. As shown in FIG. 4, when the piston 54 is extended to its balllocking position, the lower end of the piston engages and inwardlyprojecting annular lip 86 on the bottom end of the collar 76.

A tubular sealing piston assembly 90 is supported within the body 26 andfitting 34 for axial movement between a retracted position (FIG. 2) anda fully extended position (FIG. 6) and includes a tubular lower portion92 threadably connected to a tubular upper portion 94. The portions 92and 94 define an internal axially extending passage 96, and a resilientO-ring is carried by the lower piston portion 92 above a flange 98 andforms a fluid-tight seal with the inner section 42 of the body 26. Aresilient rubber-like tubular band or seal 99 is carried by the lowerpiston portion 92 and, as shown in FIG. 5, engages the upper end surfaceof the fitting 20 when the piston assembly 90 is partially extended toform a fluid-tight seal between the piston assembly and the fitting. Thepiston assembly 90 is normally in its retracted position (FIG. 2) due tothe force exerted by a compression spring 102 which extends between theupper flange 57 of the sleeve 56 and the outwardly projecting flange 98on the lower piston portion 92. The piston assembly 90 is shifted to itsextended position in response to pressurized air supplied through a lineconnected to a threaded port 106 within the head portion 31 of the body26 and connected by a passage 107 to an annular chamber 109 surroundingthe upper portion 94 of the piston assembly.

An elongated valve member 112 is supported within the passage 96 of thepiston assembly 90 and includes a closure or head portion 114 whichcarries a resilient O-ring and is connected to a guiding stem portion117 having a cross-sectional configuration in the shape of a cross. Acylindrical portion 119 projects downwardly from the stem portion 117and is adapted to engage and open the valve stem assembly 24 within thefitting 20 (FIG. 5) when the piston assembly is partially extended. Acompression spring 121 normally urges the head portion 114 to a closedposition where the O-ring engages an internal annular shoulder or seat123 within the piston portion 92 to form a fluid-tight seal.

In operation of the dispensing tool assembly 15 described above inconnection with FIGS. 1-6, the tool assembly shown in FIG. 1 is normallysupported and counter balanced by a cable extending from a spring loadedreel (not shown) positioned along an assembly line for motor vehicles.The operator lowers the tool assembly 15 onto the fitting 20, and noresistance or insertion force is required since the balls 69 areretracted as shown in FIG. 2. After the fitting 20 is inserted into thetool assembly 15 (FIG. 2), pressurized air is supplied through the lineconnected to the port 48 to extend the ball retaining piston 54 againstthe spring 74 and to cam the balls 69 into the groove 23 (FIG. 4) sothat the coupling assembly 52 positively locks the tool assembly 15 tothe fitting 20.

Pressurized air is then supplied through the line connected to the port106 for moving the piston assembly 90 to its partially extended position(FIG. 5) where the resilient seal 99 engages the upper end surface ofthe fitting 20. When the piston assembly 90 moves to this sealingposition, the cylindrical portion 119 of the valve opening member 112depresses the valve stem assembly 24 of the fitting 20 to its openposition within the fitting. When the valve stem assembly 24 is opened,it stops further movement of the valve opening member 112 so thatfurther movement of the piston assembly 90 moves the closure portion 114to an open position. The system is first evacuated by connecting thepassage 96 and the hose 17 to a vacuum or suction pump after which apredetermined volumn of liquid refrigerant is dispensed or charged intothe system 21 also through the passage 96. Since the upper end of theupper piston portion 94 is exposed to the refrigerant, an increase inpressure of the refrigerant increases the pressure of the seal 99against the fitting 20 to provide a tighter seal.

After the refrigerant receiving system is fully charged, the pressurizedair supplied to the port 48 is released so that the piston 54 returns toits retracted position by the spring 74 to release the balls 69 fromwithin the groove 23 of the fitting 20. The continued air pressurewithin the chamber 109 moves the piston assembly 90 further downwardlywithin the sleeve 56 to its fully extended position (FIG. 6) so that thetool assembly 15 is moved upwardly from the fitting 20 by pushing thefitting 20 out of the sleeve 56.

As apparent from FIG. 4, the tool assembly 15 may be manually removedfrom the fitting 20 at any time during the evacuating and charging cyclesimply to pulling upwardly on the collar 76 which shifts the piston 56upwardly to release the balls 69 from engagement with the fitting 20.However, the automatic release and ejection of the tool assembly 15 fromthe fitting 20 by releasing the air pressure within the passage 49 whilemaintaining the pressure within the passage 107, is preferred since itdoes not require operator assistance to remove the tool assembly fromthe fitting. The upward tension on the tool assembly 15 by the counterbalancing cable reel, is effective to lift the tool assembly from thefitting after the coupling assembly 52 is returned to its releasedposition.

Referring to FIGS. 7-10 which illustrte another embodiment of adispensing tool assembly 130 constructed in accordance with theinvention, a tubular body 132 includes a tubular outer section 134, atubular inner section 136 and a tubular intermediate section 138. Anannular suction passage 141 is defined between the sections 134 and 138,and another annular refrigerant supply passage 143 is defined betweenthe sections 136 and 138. The outer section 134 includes a larger upperportion 146 which has an axially extending passage 147 connected to theannular passage 143. Another axially extending passage 149 is formedwithin the upper portion 146 and connects with the annular passage 141.An annular closure or plug member 152 extends into the upper portion 146of the body section 134 and has a flange portion 153 defining extensionsof the passages 147 and 149 which continue to corresponding internallythreaded ports 154 and 156 (FIGS. 8 & 9) formed within an annular capmember 158 secured to the outer body section 134 by a set of screws 159(FIG. 9).

The lower end portion of the inner body section 136 receives an annularvalve member 162 which defines a center passage 164 connected to thepassage 141 by a radially extending passage 167 extending through themember 162, the lower end portion of the inner body section 136 and alsothrough an annular plug member 169 projecting into the member 162. Apair of resilient O-rings form fluid-tight seals between the member 162and the inner body section 136, and another pair of O-rings surround thepassage 164 and are confined between the plug members 162 and 169. Themember 162 and 169 are normally urged downwardly by a compression spring171 within a retention sleeve 172 having small holes 173.

A passage 176 extends diagonally through the lower end portion of theinner body section 136 and connect the annular passage 143 to an annularchamber 178 defined by the lower end surface of the inner body section136 and an insert ring 181 confined within the lower end portion of theouter body section 134. A washerlike closure plate 183 is secured to thelower end surface of the members 162 and 181 and is retained by anannular coupling fitting or member 186 secured to the lower end portionof the outer housing section 134 by a three peripherally spaced screws187. A series of resilient O-rings are shown in FIG. 9 for formingfluid-tight seals between the annular members 162, 181, plate 183 andcoupling member 186.

The coupling member 186 also supports a resilient sealing tube or ring192 which is confined within a surrounding cup member 194 which ismounted within a counterbore in the member 186. The resilient ring 192is adapted to engage and form a fluid-tight seal with the upper endsurface of valve fitting 20 projecting from the refrigerant receivingsystem (not shown).

The annular coupling fitting or member 186 is part of a couplingmechanism or coupler 195 which includes a set of three circumferentiallyspaced locking dogs 196 each pivotally supported within a correspondinga radial slot within the member 186 by a cross pin 197. The member 186has a tapered or frusto-conical end surface 199 which is interrupted bythe slots, and the dogs 196 pivot between retracted positions (FIG. 8)and inwardly extended locked positions (dotted lines) where the dogs 196engage the fitting 20 within the groove 23. The dogs 196 are shiftedbetween their retracted and locked positions in response to axialmovement of a cylindrical or tubular piston 204 slidably supported onthe outer body section 134.

The lower end portion of the piston 204 receives the end portions of thecylindrical cross pins 206 (FIG. 10) which engage the does 196 formoving the dogs. The tubular piston 204 is urged to its normallyretracted position (FIG. 8), where the dogs 196 are retracted, by theforce exerted by a set of three circumferentially spaced compressionsprings 209 (FIG. 10) mounted on corresponding axially extending guidepins 210 supported by the base coupling member 186. An annular collar214 surrounds the lower end portion of the tubular piston 204 and issecured to the coupling member 186 by peripherally spaced screws 216.

A cylindrical sleeve 222 surrounds the upper end portion of the tubularpiston 204 and is secured to the upper end portion 146 of the outer bodysection 134 by a set of peripherally spaced screws 223. A set of O-ringsare carried by the upper end portion of the piston 204 to formfluid-tight seals between the piston and the outer body section 134 andsleeve 222. An axially extending passage 232 is formed within the upperend portion 146 of the outer body section 134 and connects with apassage 233 formed within the members 152 and extending to an air hosefitting 234 (FIG. 8) to direct pressurized air to the upper end of thetubular piston 204. The fitting 234 is inserted within a disc 235 and isretained by a plate 236 confined within the annular cap member 158.

A tubular liner or cylinder member 237 extends into the upper endportion of the inner body section 136 and is spaced by ribs to define anannular fluid or air receiving chamber 238. A tubular valve member 242has an enlarged head portion 244 slidably supported within the cylindermember 237. The lower end portion of the valve member 242 extends intothe center passage 164 defined within the member 162 and 169 and has atapered lower end surface. The valve member 242 is supported for axialmovement as a double-acting piston, and an elongated valve stem openingpin or member 246 is axially movable within the tubular valve member242. The opening pin or member 246 has a slightly larger tubular upperend portion 249 which extends through resilient O-ring confined withinthe member 152 and an annular piston 252 supported for axial movementwithin an upper end portion of the liner member 237.

A washer-like plate 254 is confined within a counterbore within theupper end portion of the liner member 237 and has a hole 256 whichcommunicates with a passage 258 within the plug member 152 for receivingpressurized air through a line connected to a hose receiving fitting 259(FIG. 8) for actuating the piston 252. The upper portion 249 of thevalve member 246 has an internal passage 263 which is connected by across hole 264 to a fluid chamber 267 within the upper end portion 244of the valve piston 242 and within the lower end portion of the piston252.

Pressurized fluid or air is supplied to the passage 263 and chamber 267through a cross hole 269 within the upper end portion 249 of the valveopening member 246. The port 269 is connected to an annular chamber 272within a sleeve 273, and the chamber 272 receives pressurized fluid orair through an inclined passage 274 within the plug member 152 andconnected to a hose fitting 276 within the disc 235. A passage 279 isformed within the center of the disc 235 and receives pressurized fluidor air from a supply line connected to a center fitting 281 forpressurizing the upper end of the valve opening member 246. The annularpassage 238 is connected at the bottom end of the sleeve 237 to achamber 283 located below the head portion 244 of the valve member 242,and the chamber 283 is connected to the chamber within the sleeve 172 bythe ports 173. The passage 238 and chamber 283 are connected by passages284 and 286 to a hose receiving fitting 288 within the disc 235.

In operation of the tool assembly described in connection with FIGS.7-10, the tool assembly is supported in the same manner as describedabove for the tool assembly 15, that is, by suspending the tool assemblywith a cable depending from a counter-balancing reel (not shown). Thetool assembly 130 is lowered onto the fitting 20 projecting from therefrigerant receiving system, and the coupler 195 is actuated byextending the tubular piston downwardly with pressurized air directed tothe upper end of the piston through the passages 232 and 233 and thefitting 234. When the piston 204 moves downwardly, each of the dogs 196pivots inwardly to its lock position as shown by the dotted lines inFIG. 8. When the dogs 196 engage the fitting 20, the upper end of thefitting compresses against the resilient sealing ring 192 to form afluid-tight connection between the passage 164 and the passage withinthe fitting 20.

After the coupling assembly 130 is positively attached to the fitting20, pressurized air is supplied through the center fitting 281 to shiftthe opening member 246 downwardly to open the stem valve within thefitting 20 when the upper enlarged head portion of the member 246bottoms on the plug member 152. With the fitting open, the refrigerantreceiving system is evacuated by a suction applied to the passages 164,167 and 141 and through the passage 149 and a suction line (not shown)connected to the threaded port 156 within the top cap ring 158. Afterthe system is evacuated, pressurized air is introduced through thepassage 258 and fitting 259 to shift the piston 252 and the piston headportion 244 of the valve member 242 downwardly until the piston 252bottoms within the counterbore in the liner sleeve or cylinder 237. Thisfirst step downward movement of the piston head portion 244 with thepiston 252 causes the valve member 242 to close the suction passage 167with the valve member engaging the surrounding O-rings.

After the suction passage 167 is closed by the valve member 242, thepressure of the liquid refrigerant within the annular passage 143 isincreased from its normal pressure of about 100 p.s.i. to a pressure ofabout 600 p.s.i. This higher pressure of the refrigerant within thechamber 178 is effective to raise the valve member 162 to a slightlyelevated position against the compression spring 171 until the plugmember 169 engages the lower end of the sleeve 172 within the inner bodysection 136. When the valve member 162 raises in response to the higherrefrigerant pressure, the liquid refrigerant flows through the chamber178 into the passage 164 and into the refrigerant receiving systemthrough the open fitting 20.

After a predetermined charge of refrigerant is dispensed into therefrigerant receiving system, the pressure of the refrigerant within theline connected to the port 154 is reduced back to about 100 p.s.i. Thevalve member 162 returns to its closed position by the compressionspring 171 so that the flow of refrigerant is stopped. Pressurized airis then introduced through the fitting 276 and passages 274, 272, 269,263 and 264 to the chamber 267 within the upper head portion 244 of thevalve member 242. This causes the valve member 242 to move downwardlythrough a second step until the head portion 244 bottoms on the sleeve172 within the inner body section 136. As the valve member 242 movesfurther downwardly within the passage 164, it displaces the remainingliquid refrigerant within the passage 164 into the system through thefitting 20.

While pressurized air continues to be supplied to the fitting 276 andpassage 274, the pressurized air to the fitting 281 is released so thatthe valve opening member 246 returns to its fully retracted position(FIG. 9), thereby allowing the valve stem assembly 24 within the fitting20 to close. After the fitting 20 is closed, pressurized air is suppliedthrough the fitting 288 and passages 286, 284 and 238 to the chamber 283below the head portion 244 of the valve member 242. This causes thevalve member 242 to move upwardly to return the valve member 242 and thepiston 252 to their fully retracted positions shown in FIG. 9.

When the valve stem opening member 256 and the valve member 242 arefully retracted (FIG. 9), the air pressure through the fitting 234 tothe upper end of the piston 204 is released. The compression springs 209return the piston 205 to its upper retracted position (FIG. 8) so thatthe dogs 196 are pivoted to their retracted positions to release thefitting 20 from the tool assembly 130. The upward tension on the toolassembly 130 by the counterbalancing reel, automatically raises the toolassembly to an elevated position where the tool assembly is returned toits home base ready for receiving another air conditioning system whichrequires charging.

From the drawings and the above description, it is apparent that adispensing tool assembly constructed in accordance with the presentinvention, provides desirable features and advantages. For example, eachof the tool assemblies 15 and 130 are inserted onto a fitting 20 withoutany significant inserting force. The tool assemblies then automaticallylock onto the fitting 20 and automatically proceed with opening thevalve stem within the fitting, evacuating the refrigerant receivingsystem, and directing a predetermined charge to liquid refrigerant intothe system. After charging, the tool assembly provides for automaticallyclosing the valve within the fitting 20, automatically shutting off thesupply of liquid refrigerant and then for automatically releasing thetool assembly from the fitting without requiring any operatorassistance. The tool assembly shown in FIGS. 7-10 also provides forinserting onto a fitting 20 without precise axial alignment as a resultof the surface 199 and substantially removes all of the liquidrefrigerant down to the fitting 20 so that nose of the refrigerantescapes as a vapor when the tool assembly 130 is uncoupled form thefitting 20.

While the forms of apparatus and methods herein described constitutepreferred embodiments of the invention, it is to be understood that theinvention is not limited to these precise forms of apparatus andmethods, and that changes may be made therein without departing from thescope and spirit of the invention as defined in the appended claims.

The invention having thus been described, the following is claimed:
 1. Adispensing tool assembly for connecting a refrigerant charging unit to arefrigerant receiving system having a tubular fitting with an internalmovable valve element, said tool assembly comprising a tubular bodyhaving a center axis, means supported within said body and defining anaxially extending fluid passage, means for selectively connecting asuction line and a refrigerant supply line to said passage, meansforming a fluid-tight seal between said means defining said passage andthe fitting, an elongated valve element opening member disposed withinsaid passage for axial movement, first fluid actuating means for movingsaid valve element opening member between a retracted position and anextended position where the valve element within the fitting is moved toan open position, coupling means supported by said body for movementbetween a released position and a locked position positively connectingsaid body to the fitting, a piston supported by said body for axialmovement between an extended position and a retracted position, meansconnecting said piston to said coupling means for moving said couplingmeans to said locked position in response to the application of apressurized fluid to move said piston to said extended position meansfor moving said piston to said retracted position for moving saidcoupling means to said released position to provide for convenientcoupling of said tool assembly to the fitting and automatic release ofsaid tool assembly from the fitting after the receiving system hasreceived a predetermined charge of refrigerant, a valve member supportedwithin said means defining said fluid passage within said body, saidvalve member being movable between an open position allowing refrigerantto flow through said passage and a closed position, .[.and.]. fluidactuated means for moving said valve member between said open and closedpositions.Iadd., and means for removing substantially all of therefrigerant within said fluid passage between said valve member and thefitting before removing said tool assembly from the fitting to preventthe refrigerant from escaping into the air surrounding said toolassembly.Iaddend..
 2. A tool assembly as defined in claim 1 wherein saidpiston is tubular and has an axis common with the center axis of saidbody, said coupling means including a plurality of circumferentiallyspaced movable gripping elements and supported to engage a shoulder onthe tubular fitting, and means connecting said tubular piston to saidgripping elements for moving said gripping elements into engagement withthe fitting in response to movement of said tubular piston to saidextended position.
 3. A tool assembly as defined in claim 2 wherein saidmeans for moving said piston to said retracted position comprise acompression spring for normally positioning said gripping elements ofsaid coupling means in said released position to provide for insertingsaid tool assembly onto the fitting with minimal force.
 4. A toolassembly as defined in claim 3 wherein said coupling means furtherinclude a support member supporting said gripping elements for relativemovement, and said support member defines a tapering cavity forreceiving the fitting to facilitate insertion of the tool assembly ontothe fitting without requiring precise alignment between the fitting andsaid tool assembly.
 5. A tool assembly as defined in claim 1 whereinsaid piston is tubular and surrounds said tubular body.
 6. A toolassembly as defined in claim 1 wherein said means forming a fluid-tightseal comprise a resilient sealing ring surrounding said passage, andmeans supported by said body and retaining said sealing ring.
 7. A toolassembly as defined in claim 1 wherein said valve member surrounds saidvalve element opening member and is movable axially thereon, resilientsealing means engaging said valve member and cooperating therewith toform a valve for controlling the flow of fluid within said passage, andfluid actuated means for moving said valve member on said valve elementopening member.
 8. A tool assembly as defined in claim 7 wherein saidvalve member is movable on said valve element opening member to aposition adjacent said means forming a fluid-tight seal for minimizingthe escape of refrigerant gas from said tool assembly after beingremoved from the fitting.
 9. A dispensing tool assembly for connecting arefrigerant charging unit to a refrigerant receiving system having atubular fitting with an internal movable valve element, said toolassembly comprising a tubular body having a center axis, means supportedwithin said body and defining an axially extending fluid passage, meansfor selectively connecting a suction line and a refrigerant supply lineto said passage, means forming a fluid-tight seal between said meansdefining said passage and the fitting, an elongated tubular valve memberdisposed within said passage for axial movement, an elongated valveelement opening member disposed within said valve member for axialmovement, first fluid actuating means for moving said valve elementopening member between a retracted position and an extended positionwhere the valve element within the fitting is moved to an open position,second fluid actuated means for moving said valve member on said valveelement opening member to control the flow of fluid through saidpassage, coupling means supported by said body for movement between areleased position and a locked position positively connecting said bodyto the fitting, a tubular piston supported by said body for axialmovement between an extended position and a retracted position, meansconnecting said piston to said coupling means for moving said couplingmeans to said locked position in response to the application of apressurized fluid to move said piston to said extended position, andmeans for moving said piston to said retracted position for moving saidcoupling means to said released position to provide for convenientcoupling of said tool assembly to the fitting and automatic release ofsaid tool assembly from the fitting after the receiving system hasreceived a predetermined charge of refrigerant.
 10. A tool assembly asdefined in claim 9 wherein said coupling means include a plurality ofcircumferentially spaced gripping elements pivotally supported to engagea shoulder on the tubular fitting, and means connecting said tubularpiston to said gripping elements for pivoting said gripping elementsinto engagement with the fitting in response to movement of said pistonto said extended position.
 11. A tool assembly as defined in claim 9wherein said means for moving said piston to said retracted positioncomprise compression spring means for normally positioning said grippingelements of said coupling means in said released position to provide forinserting said tool assembly onto the fitting with minimal force.
 12. Atool assembly as defined in claim 10 wherein said coupling means furtherinclude a support member supporting said gripping elements for saidpivotal movement, and said support member defines a tapering cavity forreceiving the fitting to facilitate insertion of the tool assembly ontothe fitting without requiring precise alignment between the fitting andsaid tool assembly.
 13. A tool assembly as defined in claim 9 andincluding an annular valve member surrounding said passage within saidbody, said valve member being movable between an open position allowingrefrigerant to flow through said passage and a closed position, springmeans urging said annular valve member to said closed position, and saidannular valve member being movable to said open position in response tothe pressure of the refrigerant.
 14. A tool assembly as defined in claim9 wherein said piston is tubular and surrounds said tubular body.
 15. Atool assembly as defined in claim 9 and including a second pistonsupported within said body for moving said valve member, and meansdefining passages for directing fluid to move said piston and said valvemember in both axial directions.
 16. A tool assembly as defined in claim9 wherein said tubular valve member is movable on said valve elementopening member to a position adjacent said means forming a fluid-tightseal for minimizing the volume of refrigerant gas within said passagebefore said tool assembly is removed from the fitting.
 17. A method ofcharging a liquid refrigerant into a refrigerant receiving system havinga fitting with an internal valve element and with the use of adispensing tool assembly having means defining an internal chargingpassage, comprising the steps of moving the tool assembly onto thefitting with the fitting in alignment with the charging passage,coupling the tool assembly to the fitting by moving a first fluidactuated piston forming part of the tool assembly, forming a fluid-tightseal between the fitting and the means defining the charging passage,opening the internal valve element within the fitting by moving anactuating member axially with a second fluid actuated piston within thetool assembly, connecting the charging passage to a suction line toevacuate air from the system through the fitting and the chargingpassage, connecting the charging passage to a refrigerant supply line toprovide for charging liquid refrigerant into the system through thefitting, closing the passage by moving a valve member within thepassage, closing the valve element within the fitting by moving theactuating member axially with the second fluid actuated piston,.Iadd.removing substantially all of the liquid refrigerant within thecharging passage between the valve member and the fitting beforeremoving the tool assembly from the fitting to prevent the refrigerantfrom escaping into the air surrounding the tool assembly, .Iaddend.anddecoupling the tool assembly from the fitting by moving the firstactuated piston.
 18. A method of charging a liquid refrigerant into arefrigerant receiving system having a fitting with an internal valveelement and with the use of a dispensing tool assembly having meansdefining an internal charging passage, comprising the steps of movingthe tool assembly onto the fitting with the fitting in alignment withthe charging passage, coupling the tool assembly to the fitting bymoving a fluid actuated piston forming part of the tool assembly,forming a fluid-tight seal between the fitting and the means definingthe charging passage, opening the internal valve element within thefitting by moving an actuating member axially within the tool assembly,connecting the charging passage to a suction passage within the toolassembly to evacuate air from the system through the fitting and thecharging passage, closing the suction passage within the tool assemblyby moving a first valve member within the tool assembly, connecting thecharging passage to a refrigerant supply passage by moving a secondvalve member within the tool assembly to provide for charging liquidrefrigerant into the system through the fitting, closing the refrigerantsupply passage by moving the second valve member within the toolassembly, displacing the liquid refrigerant within the charging passageby moving a member within the charging passage, closing the valveelement within the fitting by moving the actuating member axially withinthe tool assembly, and decoupling the tool assembly from the fitting bymoving the piston.
 19. A dispensing tool assembly for connecting aliquid charging unit to a liquid receiving system having a tubularfitting with an internal movable valve element, said tool assemblycomprising a tubular body having a center axis, means supported withinsaid body and defining an axially extending fluid passage, means forselectively connecting a suction line and a liquid supply line to saidpassage, means forming a fluid-tight seal between said means definingsaid passage and the fitting, an elongated valve element opening memberdisposed within said passage for axial movement, first fluid actuatingmeans for moving said valve element opening member between a retractedposition and an extended position where the valve element within thefitting is moved to an open position, coupling means supported by saidbody for movement between a released position and a locked positionpositively connecting said body to the fitting, a piston supported bysaid body for axial movement between an extended position and aretracted position means connecting said piston to said coupling meansfor moving said coupling means to said locked position in response tothe application of a pressurized fluid to move said piston to saidextended position, means for moving said piston to said retractedposition for moving said coupling means to said released position toprovide for convenient coupling of said tool assembly to the fitting andautomatic release of said tool assembly from the fitting after thereceiving system has received a predetermined charge of liquid, a valvemember supported within said means defining said fluid passage withinsaid body, said valve member being movable between an open positionallowing liquid to flow through said passage and a closed position,.[.and.]. fluid actuated means for moving said valve member between saidopen and closed positions.Iadd., and means for removing substantiallyall of the liquid within said fluid passage between said valve memberand the fitting before removing said tool assembly from the fitting toprevent the liquid from escaping into the air surrounding said toolassembly.Iaddend..